Surgery for kidney stones is traumatic, generally for the patient, and specifically for the kidney. There is a recuperation period of 6 to 12 months, and the number of surgical operations on a kidney is quite limited, generally on the order of three. After this time the kidney has a great deal of scar tissue, and is traumatized to the point where it simply ceases to function.
Lithotripters for the extracorporeal destruction of kidney stones are known, and such operations in most cases can in a finite period of time reduce a kidney stone to wet dust which is passed out with the urine. This is true whether the kidney stone is actually in the kidney, or is in the bladder, or in the ureter between the kidney and the bladder. Lithotripters generally comprise a truncated ellipsoidal reflector. The reflector is filled with a liquid, commonly water, which couples the interior of the reflector to a human body, and through the tissues of the body to the kidney stone. The reflector is provided with a spark gap at the first focus point of the ellipsoid. The ellipsoidal reflector is positioned relative to the human body so that the second focus point of the ellipsoid lies on the kidney stone. A spark across the spark gap causes a certain amount of water to be flashed into steam, accompanied with generation of a shock wave. This shock wave is focused by the ellipsoidal reflector on the second focus point, and hence on the kidney stone. A fairly rapid succession of such sparks over a period of up to an hour is sufficient to disintegrate substantially any kidney stone, whereby the kidney stone is disintegrated, and subsequentally flushed out with the urine, without the necessity of in any way invading the body. A patient can generally go home the day following such treatment.
The electrodes forming the spark gap often are made of brass. Sometimes the confronting tips of the electrodes are made of tungsten, and a combination of brass on one electrode and tungsten on another is also known. Regardless of the material the service life of a pair of electrodes is quite limited. High electric power is dissipated in each spark, and the result is that the electrodes become vaporized, pitted and worn away. It is therefore necessary to replace electrodes frequently. Considerable time is required to replace a pair of electrodes in accordance with known practice. This can occur one or more times during treatment of a patient, and a delay is detrimental to the state of mind of the patient, particularly in instances in which the patient is suspended with the ellipsoidal reflector in a water bath.